In the manufacture and design of mechanical and electronic components it is frequently necesary to evaluate the component or an entire assembly or subassembly of various components for their resistance to expected environments of use, e.g. aircraft components are desirably tested for resistance to certain types of vibration. In conducting such tests the test piece is secured to a slip plate which is slidably supported by a mass such as a granite block having an oil film surface and coupled to a programmable source of vibration such as an electrodynamic shaker. In practice, the shaker drives a shaker head, and a driver bar is interposed between the shaker head and the slip plate.
Driver bars are rigid bodies which are mounted by their base to the shaker head directly or through an adaptor, and from which a normally horizontal flange projects for connection to the slip plate.
Initially, the driver bar flange sandwiched the slip plate from above and below. In an improvement a design was invented which overlay the slip plate to facilitate separation of the slip plate from the driver bar flange without need of moving the driver bar and shaker laterally relative to the slip plate. Still later, a removable retainer was used which overlay and underlay the slip plate and the flange but which was laterally removable without moving the slip plate or the shaker head. See, for example U.S. Pat. No. 3,933,033 to Kimball and U.S. Pat. No. 4,392,381 to Martin. More recently, in U.S. Pat. No. 4,489,612 to Griggs the Kimball and Martin ideas were combined into a driver bar which had a H-section like the retainer of the Martin patent and in which one leg of the H was separable to be like the Kimball patent device.
In these developments the use of a plurality of pins to connect the driver bar flange to the slip plate at lateral series of registered holes remained a constant. Typically six or more or fewer pins were set at right angles to the slip plate and flange, and secured in place by cam means. Effective pins in these apparatus use precision camming devices to obtain adjustment and are therefore quite expensive.
The setting, lossening and resetting of multiple pins is disadvantageous in terms of labor required and for the potential of misadjustment that increases with multiple pins. Moreover, in those mentioned driver bar assemblies where directly opposed relation of the driver bar flange to the slip plate was realized, doubling of the number of pins was incurred, as two rows of pins were needed to connect the driver bar to the slip plate and shaker, thus increasing both capital and labor expense and increasing the potential for misadjustment.